Effect of varying the composition of copolymers of glycidyl methacrylate and 3‐chlorostyrene (GMC) on electron lithographic performance

The polymerization kinetics, molecular parameters, and electron lithographic response of a series of copolymers of glycidyl methacrylate (GMA) and 3‐chlorostyrene (CLS) have been determined. The polymerization rate, molecular weight, and polydispersity decrease with increasing mole fraction of 3‐chlorostyrene (XCLS). Similarly, the sensitivity of this system decreases as the percentage of CLS in the copolymer increases. The value of D for the copolymer containing 14.3 mole percent CLS is 0.45 μC/cm2 increasing to 3.2 μC/cm2 for the 54 percent CLS copolymer of equivalent molecular weight. On the contrary the wet air and O2 plasma etch rates decrease as XCLS increases. For example, the etch rate using wet air for PGMA is ∼ 30 percent greater than GMC (XCLS = 0.54). The post exposure polymerization rate decreases as the CLS content increases. The extent of the post cure reaction is dose dependent being a maximum at D = 0.64 μC/cm2 for the copolymer containing 14.3 mole percent CLS.